The present invention relates to a method of fabricating a semiconductor device and a semiconductor device fabricated by the fabrication method, and particularly to a method of fabricating a semiconductor device using nitride based compound semiconductors, which is capable of peeling an under growth layer together with a growth substrate and efficiently forming an electrode on the back surface of a first conductive type layer, and a semiconductor device fabricated by the fabrication method.
A technique of peeling semiconductor growth layers stacked on a sapphire substrate from the sapphire substrate by etching has been known. The peeling technique using etching, however, has a problem associated with a slow etching rate and damage of a crystal plane by etching.
In particular, since it is difficult to peel nitride based compound semiconductor growth layers from a sapphire substrate by wet etching, the nitride based compound semiconductor growth layers have been peeled from the sapphire substrate by dry etching such as reactive ion etching. In this case, however, since a corrosive gas is used for reactive ion etching, a crystal plane is generally damaged by the corrosive gas.
To cope with such problems caused in peeling semiconductor growth layers from a growth substrate by etching, there has been developed a method of peeling semiconductor growth layers from a growth substrate by irradiating the semiconductor growth layers with laser beams traveling from the back side of the growth substrate, to cause abrasion at the interface between the semiconductor growth layers and the growth substrate, thereby peeling the semiconductor growth layers from the growth substrate.
In the case of nitride based compound semiconductor growth layers, when the semiconductor growth layers stacked on a sapphire substrate are irradiated with laser beams traveling from the back side of the sapphire substrate, an undoped layer and a buffer layer of the semiconductor growth layers absorb the laser beams, to cause abrasion, whereby the semiconductor growth layers are peeled, together with the undoped layer and the buffer layer, from the sapphire substrate. The undoped layer and buffer layer are then etched and an electrode is formed on the back surface of a semiconductor device portion of the peeled semiconductor growth layers.
Such a peeling method using laser abrasion, however, has problems that since the undoped layer and the buffer layer on the back surface of the semiconductor growth layers peeled from the sapphire substrate have a polycrystalline or amorphous structure having a high resistance, it is not appropriate to form an electrode on the undoped layer and the buffer layer, and since the undoped layer and the buffer layer are etched, the fabrication efficiency is degraded.
In the case of forming an electrode on the back surface of a semiconductor device portion of semiconductor growth layers, if the back surface of the semiconductor growth layers is etched, the number of steps of fabricating a semiconductor device is increased, to increase the fabrication cost of the semiconductor device, thereby increasing the fabrication cost of an image display unit using the semiconductor devices.
For nitride based compound semiconductor growth layers, to form an electrode on the back surface of a device portion of the semiconductor growth layers, the back surface of the device portion cannot be etched by wet etching. Therefore, it is etched by dry etching such as reactive ion etching, with a result that an undoped layer and a buffer layer on which the electrode is to be formed are significantly damaged by a corrosive gas used for dry etching.